Global Climate Change is on the Verge of a Broad-Scale Shift that May Last Decades

The global climate may be on the verge of broad-scale change that could last for decades. Scientists have discovered that a new set of climatic conditions associated with a cooling Atlantic may be the norm in the future.

"Sea-surface temperatures in the Atlantic vary between warm and cold over time-scales of many decades," said Gerard McCarthy, one of the researchers, in a news release. "These variations have been shown to influence temperature, rainfall, drought and even the frequency of hurricanes in many regions of the world. This decadal variability, called the Atlantic Multi-decadal Oscillation (AMO), is a notable feature of the Atlantic Ocean and the climate of the regions it influences."

These climatic phases are often referred to as positive or negative AMO's. They're the result of the movement of heat northwards by a system of ocean currents. This movement of heat changes the temperature of the sea surface, which then has a profound impact on climate on timescales of 20 to 30 years. The strength of these currents, though, are determined by the same atmospheric conditions that control the position of the jet stream.

In order to better understand the changes occurring, the researchers reconstructed ocean circulation over the last 100 years from tide gauges that measure sea level at the coast. This revealed observational evidence of the link between ocean circulation and the AMO.

In this case, the researchers have found that AMO is moving to a negative phase. This means that we should expect cooler surface waters which, in turn, will bring drier summers to Britain and Ireland, accelerated sea-level rise along the northeast coast of the United States, and drought to the developing countries of the Sahel region.

The findings are published in the journal Nature.

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